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Astron. Astrophys. 333, 918-925 (1998)


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A photometric study of the field RR Lyrae stars AW Dra, AQ Lyr and CN Lyr

V. Castellani 1, 2, 3, A. Di Paolantonio 2, A.M. Piersimoni 2 and V. Ripepi 1, 4

1 Dipartimento di Fisica, Università di Pisa, Piazza Torricelli 2, I-56100 Pisa, Italy
2 Osservatorio Astronomico di Collurania, Via M. Maggini, I-64100 Teramo, Italy
3 Istituto Nazionale di Fisica Nucleare, LNGS, I-67010 Assergi, L'Aquila, Italy
4 Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli, Italy

Received 22 July 1997 / Accepted 22 December 1997

Abstract

We present CCD lightcurves for the three field RR Lyrae AQ Lyr, CN Lyr and AW Dra observed at the Teramo TNT telescope. Stellar temperatures have been derived from the observed mean colors, allowing a comparison with recent theoretical predictions on RR Lyrae lightcurves. As for the two metal rich pulsators in the sample we suggest that CN Lyr has been possibly misclassified; there is some indication that it could be conceivably a c-type pulsator. On the other hand, if CN Lyr belongs to the low amplitude, b-type fundamental pulsators, it shows a lightcurve with a slow risetime that the present theory fails to predict. AQ Lyrae appears to be a metal rich ab type pulsator, with the expected luminosity but with a lower amplitude than that predicted by theory. Finally, we find that AW Dra behaves as a metal poor fundamental (F) pulsator, crossing the instability strip well above the corresponding Zero Age Horizontal Branch (ZAHB) luminosity level.

Key words: stars: evolution – stars: fundamental parameters – stars: horizontal-branch – stars: variables: RR Lyrae

Send offprint requests to: V. Ripepi

© European Southern Observatory (ESO) 1998

Online publication: April 28, 1998

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